title: Pentoxifylline enhances the radioprotective properties of γ-tocotrienol: differential effects on the hematopoietic, gastrointestinal and vascular systems.
abstract: The vitamin E analog γ-tocotrienol (GT3) is a potent radioprotector and mitigator. This study was performed to (a) determine whether the efficacy of GT3 can be enhanced by the addition of the phosphodiesterase inhibitor pentoxifylline (PTX) and (b) to obtain information about the mechanism of action. Mice were injected subcutaneously with vehicle, GT3 [400 mg/kg 24 h before total-body irradiation (TBI)], PTX (200 mg/kg 30 min before TBI), or GT3+PTX before being exposed to 8.5-13 Gy TBI. Overall lethality, survival time and intestinal, hematopoietic and vascular injury were assessed. Cytokine levels in the bone marrow microenvironment were measured, and the requirement for endothelial nitric oxide synthase (eNOS) was studied in eNOS-deficient mice. GT3+PTX significantly improved survival compared to GT3 alone and provided full protection against lethality even after exposure to 12.5 Gy. GT3+PTX improved bone marrow CFUs, spleen colony counts and platelet recovery compared to GT3 alone. GT3 and GT3+PTX increased bone marrow plasma G-CSF levels as well as the availability of IL-1α, IL-6 and IL-9 in the early postirradiation phase. GT3 and GT3+PTX were equally effective in ameliorating intestinal injury and vascular peroxynitrite production. Survival studies in eNOS-deficient mice and appropriate controls revealed that eNOS was not required for protection against lethality after TBI. Combined treatment with GT3 and PTX increased postirradiation survival over that with GT3 alone by a mechanism that may depend on induction of hematopoietic stimuli. GT3+PTX did not reduce GI toxicity or vascular oxidative stress compared to GT3 alone. The radioprotective effect of either drug alone or both drugs in combination does not require the presence of eNOS.
authors.affiliation: Division of Radiation Health, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA.
authors.forename: Maaike
authors.initials: M
authors.lastname: Berbée
authors.forename: Qiang
authors.initials: Q
authors.lastname: Fu
authors.forename: Sarita
authors.initials: S
authors.lastname: Garg
authors.forename: Shilpa
authors.initials: S
authors.lastname: Kulkarni
authors.forename: K Sree
authors.initials: KS
authors.lastname: Kumar
authors.forename: Martin
authors.initials: M
authors.lastname: Hauer-Jensen
mesh_terms: D000818:Animals; D001808:Blood Vessels / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects; D002839:Chromans / Q000494:pharmacology*; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006410:Hematopoiesis / Q000187:drug effects* / Q000528:radiation effects; D007422:Intestines / Q000187:drug effects* / Q000528:radiation effects; D008297:Male; D051379:Mice; D018384:Oxidative Stress / Q000187:drug effects / Q000528:radiation effects; D010431:Pentoxifylline / Q000494:pharmacology*; D030421:Peroxynitrous Acid / Q000096:biosynthesis; D011832:Radiation Injuries / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D016019:Survival Analysis; D057772:Vascular System Injuries / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control; D014810:Vitamin E / Q000031:analogs & derivatives* / Q000494:pharmacology; D014916:Whole-Body Irradiation / Q000009:adverse effects
chemical_list: D002839:Chromans; D004791:Enzyme Inhibitors; D011837:Radiation-Protective Agents; D014810:Vitamin E; D030421:Peroxynitrous Acid; C013649:plastochromanol 8; D010431:Pentoxifylline